Thermostatic control valve with fluid mixing

ABSTRACT

A thermostatic control valve assembly for use in continuously mixing a hot first fluid with a cold second fluid to continuously produce a mixed fluid at a constant temperature. The valve assembly includes an improved mixing dome defining a mixing chamber that facilitates thorough mixing of the hot and cold fluids over a wide range of flow rates, including rates as low as two gallons per minute. The improved mixing performance is accomplished by a plurality of baffles sequentially disposed along the flow path within the mixing chamber and extending at an angle in opposition to the flow path. Each baffle exhibits a paisley shape and is angularly displaced from the adjacent baffles to turn the fluid flow, thereby optimally mixing the hot and cold fluids over a wide range of flow rates while minimizing the pressure drop between the valve inlet and outlet.

BACKGROUND OF THE INVENTION

[0001] The present invention relates to the field of fluid mixing valveassemblies. More particularly, the invention concerns an improvedthermostatically controlled mixing valve assembly in which a thermostatis immersed in the fluid flowing through the valve.

[0002] Thermostatic control valve assemblies are well known in the artand have long been utilized in various applications including groupshowers, washing stations, hospital hydrotherapy installations and inmany industrial applications where precision thermostatic water blendingis essential. In order to operate properly, the hot and cold waterentering such a valve assembly must be thoroughly blended before thetemperature of the mixture is sensed by the thermostat. If the hot andcold water are not adequately mixed, the valve assembly can behaveerratically because the temperature sensor sees pockets of hot and coldwater instead of a mixture that is at a single temperature throughout.One problem that has long persisted in the art is the inability of mostvalve assemblies to adequately mix the hot and cold water over a widerange of flow rates. Consequently, multiple valves often have to be usedto satisfy flow requirements.

[0003] Another problem that has persisted in the art is the physicalsize of the valve assembly required for a specific application. Often,the valve assembly is simply too large because of the need for a largemixing chamber to adequately mix the hot and cold water. What is neededis a thermostatic control valve assembly having an improved mixingchamber that has the ability to thoroughly mix the hot and cold waterover a wide range of flow rates, and which does so in a smaller physicalspace than valve assemblies currently known in the art.

[0004] One such valve assembly featuring an improved mixing chamber isdisclosed in U.S. Pat. No. 5,203,496 which is assigned to the assigneeof the present invention. It is now desired to improve the operation ofsuch valve assemblies by providing a mixing valve assembly whichoperates with reduced pressure drop across the valve assembly, whilestill thoroughly mixing the hot and cold fluids.

SUMMARY OF THE INVENTION

[0005] A thermostatic control valve assembly for continuously mixing ahot first fluid with a cold second fluid to continuously produce a mixedfluid at a constant temperature according to one embodiment of thepresent invention comprises a cold fluid inlet, a hot fluid inlet, amixing dome defining a mixing chamber, a thermostatically controlledflow control valve and an operably connected thermostat for adjustingthe flow of the hot and cold fluids into the mixing chamber. The mixingdome includes a plurality of baffles sequentially placed in the flowpath to promote better mixing of the hot and cold fluids before themixed fluid contacts the thermostat disposed in the fluid flow path.

[0006] In one aspect of the invention, each baffle projects into theflow stream and is angled from the mixing dome wall in a directioncontrary to the direction of flow. The mixing performance is furtherimproved by angularly displacing the each baffle with respect to eachother to impart a twisting movement to the fluid. The mixing domeincludes means for supporting the thermostat between the baffles and thefluid outlet of the dome.

[0007] A general object of the present invention is to provide animproved thermostatic control valve assembly. A specific object is toprovide a valve assembly that more efficiently mixes hot and cold fluidsfor accurately sensing the temperature of the mixture.

[0008] A further objective is to provide a valve assembly that provideseffectively mixed hot and cold fluids with reduced pressure drop betweenthe valve and valve outlet. Related objects and advantages of thepresent invention will be apparent from the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 shows a side cross-sectional view of a thermostatic controlvalve assembly according to a preferred embodiment of the presentinvention.

[0010]FIG. 2 shows a side cross-sectional view of a housing defining animproved mixing chamber for the valve assembly shown in FIG. 1.

[0011]FIG. 3 is a top view along section 3—3 of FIG. 2 showing a firstbaffle according to the present invention.

[0012]FIG. 4 is a top view along section 4—4 of FIG. 2 showing a secondbaffle according to the present invention.

[0013]FIG. 5 is a top view along section 5—5 of FIG. 2 showing a thirdbaffle according to the present invention.

[0014]FIG. 6 shows a side cross-sectional view of a housing defining animproved mixing chamber for a second embodiment of the presentinvention.

[0015]FIG. 7 is a top view along section 3-3 of FIG. 6 showing a firstbaffle according to the present invention.

[0016]FIG. 8 is a top view along section 4-4 of FIG. 6 showing a secondbaffle according to the present invention.

[0017]FIG. 9 is a top view along section 5-5 of FIG. 6 showing a thirdbaffle according to the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0018] For the purposes of promoting an understanding of the principlesof the invention, reference will now be made to the embodimentillustrated in the drawings and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the invention is thereby intended, such alterations andfurther modifications in the illustrated device, and such furtherapplications of the principles of the invention as illustrated thereinbeing contemplated as would normally occur to one skilled in the art towhich the invention relates.

[0019] Referring now to FIG. 1, there is shown a thermostatic controlvalve assembly 10 with fluid mixing according to the preferredembodiment of the present invention. Valve assembly 10 includes a hotinlet 11, a cold inlet 12 and an outlet 13. Inlets 11 and 12 areconnected to opposite sides of flow control valve 14 and open to annularcavities 15 and 16, respectively, within the flow control valve. Theinner wall of annular cavities 15 and 16 is defined by a cylindricallyshaped liner 17. Liner 17 is open at both ends and includes a pluralityof openings or slots 18 which are distributed around its circumferencein communication with cavities 15 and 16.

[0020] Slidably mounted within liner 17 is a cylindrically shaped piston19 which is open at its upper end. Piston 19 is preferably pressurebalanced and includes a plurality of openings or slots 20 that aredistributed around its circumference. Preferably, each opening 20through piston 19 has a counterpart opening 18 in liner 17. Modulationof the piston 19 within the liner 17 variably opens the cavities 15 and16 to the interior of the piston 19, which communicates the combined hotand cold fluid to the outlet 14 a of the flow control valve.

[0021] Flow control valve 14 also includes a bottom plug 21 which can beremoved to allow access to repair, replace or clean the interior partsof flow control valve 14. Bottom plug 21 defines a cavity 22 thereinwhich substantially receives compressed valve spring 23. Valve spring 23is supported at one end by bottom plug 21 and is connected at its otherend to the base 24 of piston 19. The spring 23 applies a return force topiston 19.

[0022] A push rod 25 extends through the liner 17 and piston 19 toengage the base 24. The opposite end of push rod 25 is connected to athermostat 26. Thermostat 26 can be of many types known in the art, suchas a thermal coil or a temperature sensitive bellows. Such a thermostatis designed to expand or contract along the axis defined by push rod 25in linear proportion to a change in the temperature of fluid surroundingthe thermostat. In this embodiment, thermostat 26 is connected toadjustment screw 27 via shaft 28. Adjustment screw 27 acts againstspring 23 and thus allows the vertical position of the thermostat 26,and ultimately of the piston 19, to be adjusted, which in turn altersthe relative proportions of hot and cold fluid passing through openings20.

[0023] One problem that has persisted in the art is the inability ofvalve assemblies to operate properly over a wide range of flow rates. Inother words, a flow control valve assembly is only useful over the rangeof flow rates that the device is able to thoroughly blend the hot andcold fluids before the mixture contacts the thermostat. While many knownmixing valve assemblies are capable of adequate fluid mixing at highflows, a need remains for a valve assembly that is also capable ofthorough hot and cold fluid mixing at low flow rates, such as below 10g.p.m.

[0024]FIG. 1 illustrates one form of control valve assembly that mayutilize the features of the present invention. It is understood that theinvention can have application with a variety of thermostat controlvalve configurations. In the illustrated embodiment, a mixing dome 29 isengaged over the outlet 14 a of the flow control valve 14. The mixingdome 29 defines a mixing chamber 30 therein which is preferablycylindrical in configuration. An important feature of the presentinvention is the incorporation within the mixing dome 29 of means forturning or rotating the fluid flow through the mixing chamber 30 toensure complete mixing of the hot and cold fluid before it reaches thethermostat 26. Complete fluid mixing assures a uniform temperaturethroughout the fluid discharged through outlet 13. Most importantly, themixed fluid accurately reflects the exiting temperature of the fluid sothe thermostat can accurately regulate the movement of the valve controlelements.

[0025] According to the invention, the means for turning the fluidincludes a plurality of baffles 31 that are integrally formed as part ofthe housing 32 forming the mixing dome. The shape and relativearrangement of baffles 31 are intended to induce more thorough blendingof the hot and cold fluids in mixing chamber 30 before the mixturecontacts thermostat 26, particularly at low flow rates where the problemof inadequate mixing is most prevalent.

[0026] In order to reliably react to a change in the temperature of thefluid mixture, the thermostat must be immersed in the mixture, and themixture must have a substantially uniform temperature throughout ratherthan consisting merely of hot and cold pockets. Baffles 31 of thepresent invention create a vortex in the fluid flow so that the hot andcold fluids remain in contact longer, leading to complete mixingresulting in a substantially uniform fluid mixture and temperature priorto flowing around the immersed thermostat. In this manner, higher flowrates are achieved with only a minimal pressure drop between the valveinlet and outlet.

[0027] The mixing dome 29 is shown in more detail in FIG. 2. The housing32 defines the mixing chamber 30 therein and a flow path 33therethrough. The housing 32 is provided with a mating surface 35 and anannular flange 36 that enable the housing to be mated to flow controlvalve 14 by conventional means. Housing 32 also defines an opening 37 atits top which permits an adjustment means, such as screw 27 and shaft28, to be connected to the thermostat, as better shown in FIG. 1. Inoperation, the fluid leaving flow control valve 14 enters housing 32through inlet 34. Immediately afterwards, the fluid encounters baffles38, 39 and 40 in successive order. The fluid mixture then continuesupward along flow path 33 until finally exiting housing 32 throughoutlet 13.

[0028] The outlet 13 is positioned at the end of the mixing chamber orfluid flow path to ensure that the thermostat 26 is substantiallyimmersed in the fluid exiting the valve assembly 10. Moreover, thethermostat 26 is disposed downstream of the sequential baffles,preferably by a distance greater than the distance between successivebaffles. Thus, the hot and cold fluids are substantially mixed prior tothe thermostat, and substantially all of the thermostat is exposed tothe fluid mixture to assure that the thermostat receives a properindication of the temperature of the exiting fluid.

[0029] A more detailed view of each baffle is provided in the sectionedviews of FIGS. 3, 4 and 5. Although not shown in FIG. 2, it should benoted that if the vertical spacing of the baffles is sufficiently close,the baffles will overlap so that a section taken through the housingwill encompass more than one baffle. As best shown in FIG. 5, eachbaffle is preferably curved in shape having a rounded first end 44 and asecond end 46 that tapers into the wall of the housing 32. The bafflesrun about 210 degrees end to end. Each baffle is angled downward counterto the direction of fluid flow, preferably at an angle of about 70degrees as shown in FIG. 2. This arrangement imparts a turning action onthe fluid stream, facilitating mixing of the hot and cold fluids. Thebaffles are most preferably arranged so that the tapered end 46 of thebaffles meet the fluid first. This minimizes turbulence and reducespressure drop as the fluid maintains laminar flow along the graduallywidening baffle. The housing 32 and baffles may be manufactured byconventional casting techniques, such as sand casting.

[0030] Each baffle is rotationally displaced from each adjacent baffleto produce a helical arrangement of baffles 38, 39 and 40 in flow path33. In this embodiment, each successive baffle is rotated through anangle 48, which in the illustrated embodiment is 120 degrees, to producea generally helical flow path through the baffles. The helical patternof successive baffles creates an overall amount of mixing which isgreater than the sum of the individual baffles acting alone and withoutexcessive pressure drop.

[0031] In one specific embodiment of the invention, the housing 32 is ofsand-cast bronze and defines a cylindrical mixing chamber 2.0 inches indiameter and about 10.0 inches in length from the base of the mixingchamber to the center of the outlet opening 13. The baffles in thisspecific embodiment can be spaced about 1 inch apart. Each baffle canhave a maximum width of about ⅝ inches. Each baffle can have a totalsurface area that is about one-half the cross sectional area of thechamber.

[0032] Preferably, the baffles define an unobstructed center opening 49along the subtended length of the housing. In a specific embodiment,this opening 49 can have a diameter of ¾ inches for a 2 inch housing Ina most preferred embodiment, the baffles assume a “paisely” shape tocreate the center opening and provide a smooth flow transition up eachbaffle. The valve assembly 10 of the specific embodiment is capable ofaccurately controlling the outlet fluid temperature at flows of 2-80g.p.m. The fluid mixing provided by the baffles is particularlyimportant at the low flow rates since the fluid flow can “short-circuit”the thermostat in which the entire thermostat is not immersed in thefluid flow prior to the outlet 13.

[0033] Another embodiment of the invention is shown the mixing dome 29shown in FIG. 6. The housing 32 defines the mixing chamber 30 thereinand a flow path 33 therethrough as previously described.

[0034] A more detailed view of each baffle in this embodiment isprovided in the sectioned views of FIGS. 7, 8 and 9. Each baffle iscrescent shaped and is angled downward counter to the direction of fluidflow, preferably at an angle of between 45 and 70 degrees. Again, thehousing 32 and baffles 38′, 39′, and 40′ may be manufactured byconventional casting techniques, such as sand casting.

[0035] Each baffle is rotationally displaced from each adjacent baffleto produce a helical arrangement of baffles 38′, 39′ and 40′ in flowpath 33. In this embodiment, each successive baffle is rotated throughan angle 48′, which in this case is about 45 degrees, to produce agenerally helical flow path through the baffles. Each baffle defines achord 41, 42, and 43 between its end points which is useful inillustrating the helical arrangement of the baffles in the flow path. InFIGS. 7-9, chords 42, 42, and 43 are show with their respectiveperpendicular bisectors successively rotated by an angle of about 45degrees. The helical pattern of successive baffles creates an overallamount of mixing which is greater than the sum of the individual bafflesacting alone and without excessive pressure drop.

[0036] While the invention has been illustrated and described in detailin the drawings and foregoing description, the same is to be consideredas illustrative and not restrictive in character, it being understoodthat only the preferred embodiment has been shown and described and thatall changes and modifications that come within the spirit of theinvention are desired to be protected.

[0037] For instance, in the preferred embodiment, the baffles 38, 39 and40 are integrally formed in the housing 32 by known casting techniques.The invention further contemplates that each baffle constitutes aseparate element that is suitably mounted within a cylindrical cavity inthe housing. For instance, the separate baffles could be snap fittedwithin grooves formed in the housing.

[0038] Moreover, the invention contemplates incorporating additionalbaffles sequentially disposed along the flow path. Multiple housingsections can be combined, and more baffles can be added to the longerchamber. The additional baffles would preferably be arranged in thehelical pattern described above. Thus, while the baffles of thepreferred embodiment are rotated 120 degrees relative to each other, theaddition of more baffles permit smaller relative angular displacementsbetween consecutive baffles.

What is claimed is:
 1. A thermostatic control valve assembly for mixinga hot fluid and a cold fluid for discharge at a controlled temperature,the valve assembly comprising: a cold fluid inlet; a hot fluid inlet; aflow control valve for controllably mixing hot and cold fluid receivedthrough said hot fluid inlet and said cold fluid inlet, respectively; ahousing defining a fluid outlet and a mixing chamber providing a fluidflow path between said flow control valve and said outlet; at least twobaffles sequentially arranged and angularly displaced from each other insaid flow path within said housing for turning the fluid flow throughthe mixing chamber, each of said baffles projecting at anon-perpendicular angle into said flow path; and a thermostat disposedwithin said mixing chamber between said at least two baffles and saidfluid outlet and operably connected to said flow control valve tocontrol said flow control valve in response to the temperature of fluidflowing through said mixing chamber.
 2. The thermostatic control valveassembly of claim 1 further including a third baffle angularly displacedfrom each of said at least two baffles.
 3. The thermostatic controlvalve assembly of claim 2 wherein said baffles project at an angle ofabout 70 degrees.
 4. The thermostatic control valve assembly of claim 2wherein said baffles define an arcuate inner edge.
 5. The thermostaticcontrol valve assembly of claim 4 wherein said baffles define a paisleyshape.
 6. The thermostatic control valve assembly of claim 5, whereineach of said baffles is consecutively angularly displaced by an angle ofabout 120 degrees.
 7. The thermostatic control valve assembly of claim 4wherein said baffles define a crescent shape.
 8. The thermostaticcontrol valve assembly of claim 7, wherein each of said baffles isconsecutively angularly displaced by an angle of about 45 degrees.
 9. Amixing dome for use in a thermostatic control valve assembly having ahot fluid inlet, a cold fluid inlet, a thermostatically controlled flowcontrol valve combining hot and cold fluid received through therespective inlets, a thermostat operably coupled to the flow controlvalve for adjusting the amount of hot and cold fluid combined inresponse to the temperature of the fluid mixture, said mixing domecomprising: a housing defining an inlet, an outlet and a mixing chamberproviding a fluid flow path between said inlet and said outlet; at leasttwo baffles sequentially arranged and angularly displaced in said flowpath and integrally formed in said housing for turning the fluid flowthrough the mixing chamber, each of said baffles projecting at anon-perpendicular angle into said flow path; wherein said inlet of saidhousing is configured to mate with the outlet of the flow control valve;and wherein said mixing chamber is sized to receive the thermostatbetween said at least two baffles and said outlet of said housing. 10.The mixing dome of claim 9 further including a third baffle angularlydisplaced from each of said at least two baffles.
 11. The mixing dome ofclaim 10, wherein said baffles project at an angle of about 70 degrees.12. The mixing dome of claim 10 wherein said baffles define an arcuateinner edge.
 13. The mixing dome of claim 12 wherein said baffles definea paisley shape.
 14. The mixing dome of claim 13, wherein each of saidbaffles is consecutively angularly displaced by an angle of about 120degrees.
 15. The mixing dome of claim 12 wherein said baffles define acrescent shape.
 16. The mixing dome of claim 15, wherein each of saidbaffles is consecutively angularly displaced by an angle of about 45degrees.
 17. A mixing dome for a thermostatic control valve assemblycomprising: an elongated cylindrically shaped housing open at one endand defining a cavity therein for receiving a thermostat and alsodefining an outlet opening to said cavity remotely located from said oneend, said one end having means for mating said housing to a flow controlvalve, said housing including at least two baffles integrally formedtherein, sequentially positioned and angularly displaced within saidcavity near said one end, and each of said at least two bafflesprojecting at a non-perpendicular angle from said housing.
 18. Themixing dome of claim 17 further including a third baffle angularlydisplaced from each of said at least two baffles.
 19. The mixing dome ofclaim 18, wherein said baffles project at an angle of about 70 degrees.20. The mixing dome of claim 18 wherein said baffles define an arcuateinner edge.
 21. The mixing dome of claim 20 wherein said baffles definea paisley shape.
 22. The mixing dome of claim 21, wherein each of saidbaffles is consecutively angularly displaced by an angle of about 120degrees.
 23. The mixing dome of claim 20 wherein said baffles define acrescent shape.
 24. The mixing dome of claim 23 wherein each of saidbaffles is consecutively angularly displaced by an angle of about 45degrees.
 25. A mixing dome for a thermostatic control valve assemblycomprising: an elongated cylindrically shaped housing open at one endand defining a cavity therein for receiving a thermostat and alsodefining an outlet opening to said cavity remotely located from said oneend, said one end having means for mating said housing to a flow controlvalve, and said housing including at least two baffles integrally formedtherein, sequentially positioned and angularly displaced within saidcavity near said one end, each said baffle exhibiting a curved inneredge wherein said baffles cooperate to create a substantiallycylindrical unobstructed central flow path within said cavity, andwherein each of said baffles project at a non-perpendicular angle fromsaid housing.
 26. The mixing dome of claim 25, wherein said bafflesproject at an angle of about 70 degrees.
 27. A mixing dome for athermostatic control valve assembly comprising: an elongatedcylindrically shaped housing open at one end and defining a cavitytherein for receiving a thermostat and also defining an outlet openingto said cavity remotely located from said one end, said one end havingmeans for mating said housing to a flow control valve, and said housingincluding at least two helically arranged baffles integrally formedtherein, sequentially positioned and angularly displaced within saidcavity near said one end, wherein said baffles cooperate to create asubstantially cylindrical unobstructed central flow path within saidcavity.
 28. A baffle for a mixing dome housing, said baffle comprising:a leading downstream edge tapered into the housing; an upstream edgewider than said downstream edge; and an arcuate portion connecting saidupstream and downstream edges.
 29. The baffle of claim 28 wherein saidbaffle runs about 210 degrees from said downstream edge to said upstreamedge.
 30. The baffle of claim 28 wherein said baffle has a surface areathat is about one-half the cross sectional area of the housing.
 31. Thebaffle of claim 28 wherein said baffle has a paisley shape.